Yeah, even for a 1200W kettle heating a liter of water can be faster in the kettle than an average gas stove and pot.

Yeah it's just not. I have one of those ridiculous bazillion-BTU gas burners and I still prefer to boil water using a combination of a 120V tea kettle (1L) and an 120V portable induction cooker. An installed 240V range is even faster, but I don't have one of those.